It used to be possible to record the output of any other program using either SoundFlower or Jack to route them into Amadeus. Unfortunately, these pieces of software have been discontinued and there currently seem to be only rather expensive commercial solutions available for routing audio between apps on macOS X in a reliable way.

However, the main reason why users would use such software in the first place was to extract the audio stream from YouTube videos. It turns out that this is still possible using the free software VLC available here:http://www.videolan.org/vlc/. Here is how this goes:

1. Navigate to the YouTube video in Safari and copy its URL from the address bar.

2. Open VLC, choose "File -> Open Network", paste the URL in there and click "Open".

3. The video will start playing immediately, so stop playback by clicking on the square "Stop" button.

4. Choose "File -> Convert/Stream" and drag the video from the main playlist window onto the area marked "Drop media here".

5. Select the profile "Audio - CD", click on "Save As File", and choose a filename and location.

6. Hit "Save" and wait until the conversion is complete and presto, you now have a Wave file with the audio track of your YouTube video which you can edit / convert using Amadeus Lite.

In principle, other conversion options are available, but neither Mp3, nor FLAC worked for me, so the easiest is to just export the audio as a Wave file and to convert it to another format later if needed. Hope this helps! Best,